1. Field of the Invention
This invention relates to an electronic still camera for recording images on a semiconductor memory card used as a recording medium.
2. Description of the Related Art
Recently, electronic still cameras which use a solid state imaging device, such as a charge coupled device (CCD) for photographing still images of subjects and recording the still images on rotatable magnetic recording medium, are considered to replace conventional still cameras for photographing and recording still images by use of the photosensitivity of photographic films, and they have been merchandised. However, since this type of electronic still camera uses the rotatable magnetic recording medium, a driving unit for driving the rotatable magnetic recording medium relative to the recording head must be provided inside the camera, thus making it difficult to reduce the size of the camera. A solid state electronic still camera system for recording image signals on a memory card using a semiconductor memory has been proposed, as a system which has no driving unit and is suitable for small sized cameras, by the same applicant (Minoru Sasaki U.S. application No. 073.160). An example of this type of electronic still camera is shown in FIG. 13.
An image of the subject is transmitted via lens 121, diaphragm 122 and color filter 120, formed on CCD 126 used as the imaging device in which the image is subjected to the photoelectric conversion. An output signal of CCD 126 is subjected to a predetermined process in pre-processing circuit 127, converted into a digital signal by means of analog-to-digital (A/D) converter 128, and then recorded on memory card 115. In this case, a signal of each picture element of the imaging device is recorded in the digital form on memory card 115. The signal of each picture element of the imaging device is subjected to a predetermined process such as amplification, white-balance correction and .gamma. correction as the pre-processing noted above. Picture element data which has been subjected to the pre-processing in a sequence according to the picture element array is recorded on memory card 115. In the reproduction mode, memory card 115 is set in a reproducing unit, and data stored in memory card 115 is subjected to a predetermined signal processing and digital-to-analog (D/A) conversion, and then supplied to a TV (television) monitor which in turn displays the data as an image. In FIG. 13, case 110, release switch 111, battery 123 used as a power source, shutter control circuit 124 for controlling diaphragm 122 and electronic shutter operation, CCD driving circuit 125, and monitoring unit 130 are also shown. CCD driving circuit 125 is used to control and drive shutter control circuit 124, CCD 126, pre-processing circuit 127, A/D converter 128 and memory card 115. Monitoring unit 130 displays the photographed image based on signals transmitted via pre-processing circuit 127 at the time of photographing and is used as a view.
As described above, wherein data corresponding to each picture element of the solid state imaging device is recorded on the memory card, the signal processing is simple and the device is simple in construction. However, if the recording conditions, such as the number of picture elements and the arrangement of color filters of the solid state imaging device of the electronic still camera, are changed, for example, the arrangement of data recorded on the memory card will be changed accordingly. Therefore, the recorded memory card is not interchangeably used for another type of electronic still camera system, that is, an electronic still camera having a different number of picture elements and arrangement of color filters from those of the electronic still camera originally used for recording the image data on the memory card.
If a single electronic still camera is designed so as to record an image under different recording conditions, the recorded memory card may be interchangeably used to some extent. However, in this case, the memory capacity required for recording one frame of image data of the photographed still image varies depending on the recording conditions set at the time of photographing. Therefore, in a case where new image data is written into a recording area in which one frame of image data has been recorded and erased, the memory capacity may some sometimes be insufficient for recording the new image data, thus making it impossible to record the new image data.